Oliver James: We're all optimists at heart. We have to be, or we'd go mad

Our collective feelings of insecurity and horror after the American atrocity will disappear with astonishing rapidity. Even if a war or other similar retribution keeps the historic event in our consciousness, the emotions you feel now will soon be a distant memory.

Consider how quickly you adjusted to the end of the Cold War. I can remember sitting in Hyde Park aged 16, in 1970, imagining what it would be like to see the skyline implode. Most people who lived through that time pictured the mushroom cloud rising. The apocalyptic vision recurred in dreams, literature and art. Yet when was the last time you conceived of nuclear immolation? Probably, not for years.

Or consider your response to the deaths of Diana, Princess of Wales, or John Lennon. You may still recall where you were when you heard the news, but I expect you have to work hard to conjure up the feelings.

Last week's terrible events may cause the world economy to be depressed but it will not cause the global psyche to be trapped in pessimistic despair. T S Eliot was spot on when he wrote that "human-kind cannot bear very much reality". We ensure we do not succumb to madness by believing that friends admire us more than they really do or that bad things are less likely to happen than is actuarially the case. And if our rose-tinted bubble of positive illusions is ever punctured, a new one soon replaces the old.

The American atrocity will have temporarily popped our illusion that the world order is safe. And yet, despite the recent evidence that it is indisputably fragile, we persuade ourselves, as a default position, that "it will all be all right in the end".

Television and rapid communications meant that many of us saw the plane smash into the tower blocks of the World Trade Centre. All of us will have pictured what it would have been like to be on board, stimulated by the accounts of passengers making their last vows of love to intimates on their mobile phones.

It was evil genius on the part of the murderers to encourage these calls because it fixes the experience deep in our psyches. For a time, most of us will feel nervous boarding a plane or visiting a conspicuous capitalist landmark such as Canary Wharf in London. And yet, by this time next year, only the most anxious of us will not have created a new bubble of positive illusions that enable us to travel by air without concern or to visit skyscrapers.

As a new book chronicles (Cultural Pessimism, by Oliver Bennett), we live in a time that is particularly packed with narratives of despair: economic, ecological, psychological. In my last book I said that America was in the same state of vulnerability to revolutionary change as Russia was in 1905.

But nothing will stop me or you from continuing to believe that our children have a future, from believing that things will probably be OK. In the face of the most dreadful evidence that the pessimist is right about the human condition, most of us remain optimists at heart. Without that instinctive hope, there would be no point in the human condition at all.

Oliver James is a clinical psychologist and author 'Britain on the Couch'